Alpine vegetation is scarce in central Mexico (≈150 km²) and occurs on the 11 highest peaks of the Trans-Mexican Volcanic Belt (TMVB). Timberline occurs at (3700) 3900 m, and at 4750 m vascular plants cease to exist. The alpine vascular flora comprises 237 species from 46 families and 130 genera. Asteraceae (44), Poaceae (42), and Caryophyllaceae (21) possess 45% of the species; none of the remaining families have more than 10 species. Four species are strict endemics, and eight others are near endemics. Thirteen species are restricted to alpine vegetation but also occur outside the study area. Seventy-seven species are endemic to Mexico, 35 of which are endemic to the TMVB. In terms of biogeography, the strongest affinities are with Central or South America. Fifteen species are also native to the Old World. Size of the alpine area seems to not be the determining factor for its floristic diversity. Instead, the time since and extent of the last volcanic activity, in addition to the distance from other alpine islands, appear to be important factors affecting diversity. There is evidence for upward vegetational shifts having occurred during the last century.

The subtribe Ditaxinae in the plant family Euphorbiaceae is composed of five genera (Argythamnia, Caperonia, Chiropetalum, Ditaxis and Philyra) and approximately 120 species of perennial herbs (rarely annual) to treelets. The subtribe is distributed throughout the Americas, with the exception of Caperonia, which also occurs in tropical Africa and Madagascar. Under the current classification, Ditaxinae includes genera with a questionable morphology-based taxonomy, especially Argythamnia, Chiropetalum and Ditaxis. Moreover, phylogenetic relationships among genera are largely unexplored, with previous works sampling <10% of taxa, showing Ditaxinae as paraphyletic. In this study, we inferred the phylogenetic relationships within Ditaxinae and related taxa using a dataset of nuclear (ETS, ITS) and plastid (petD, trnLF, trnTL) DNA sequences and a wide taxon sampling (60%). We confirmed the paraphyly of Ditaxinae and Ditaxis, both with high support. Following our phylogenetic results, we combined Ditaxis in Argythamnia and upgraded Ditaxinae to the tribe level (Ditaxeae). We also established and described the tribe Caperonieae based on Caperonia, and transferred Philyra to the tribe Adelieae, along with Adelia, Garciadelia, Lasiocroton and Leucocroton. Finally, we discuss the main morphological synapomorphies for the genera and tribes and provide a taxonomic treatment, including all species recognized under each genus.

Societal Impact Statement: Alternative crops are a promising approach to address the global food shortage that is exacerbated by climate change and wealth disparities. Some of these alternative crops are traditional food plants that have been widely traded for centuries, whereas others have only recently become more popular. Chía is a traditional native “superfood” that is the fruit of three distinct mint species. Chía (Salvia hispanica) is commercially cultivated and shares nutritional properties with California thistle sage (Salvia carduacea) and desert chía (Salvia columbariae). These wild relatives of S. hispanica are adapted to arid conditions and have potentially valuable genetic variation for the development of chía agricultural varieties. The development of nutritious, drought‐tolerant crops such as chía will increase the resilience of people to the impact of climate upheaval.Summary: In the Spanish language, the word chía refers to the nutlet fruits of several Salvia species native to Mesoamerica. The process of domestication of S. hispanica altered several traits, including the absence of shattering fruits, which makes harvest easier and mechanizable. S. hispanica is commercially cultivated in Mexico, South America, Australia, and less so in Europe and Africa. Other edible chía species are not commercially cultivated, including S. carduacea, and S. columbariae. These Californian chías are traditionally harvested by hand since the fruiting calices shatter and release the nutlets. Here we compare these three edible chía species, review their uses by native peoples, describe their morphology, summarize their natural distributions and cultivation, and provide an identification key. Native peoples in North America have traditionally used chías for food, medicine, and oil. S. hispanica naturally occurs throughout areas of Mexico that receive summer monsoonal rains. As such, it is a summer annual with an erect habit and cauline, simple leaves. In contrast, the Californian chía species are distributed through areas of the Mojave and Sonoran deserts that receive winter rains. They are winter annuals and their rosettes of lobed, pubescent leaves are typical adaptations to arid conditions. Nutlets in these chía species are similar when dry, but cultivated S. hispanica nutlets produce extensive mucilage when wetted, while the other chía produce mucilage to a lesser extent. As consumer interest grows in superfoods like chía, crop breeders may use wild chía to breed varieties appropriate for areas affected by drought or in desert agroecological systems.

Background: Euphorbiaceae is one of the largest angiosperm families in Mexico, but our understanding of its diversity and distribution is incomplete, and most genera lack taxonomic revisions. Questions: How many genera and species of Euphorbiaceae occur in Mexico, and which of these are endemic to the county or a particular state? Where is the greatest diversity? Study site and years of study: Mexico, 1990s-present. Methods: Pertinent Euphorbiaceae literature was reviewed, and major herbaria were consulted, as too was the iNaturalist platform. This information was supplemented by fieldwork. Results: Euphorbiaceae is the fifth most diverse family in Mexico, where 32 genera and 713 species occur natively. Eleven species and two genera (Ricinus y Mercurialis) are naturalized. Four genera contain almost 75 % of the species (Euphorbia, 245 spp., Croton, 130 spp., Acalypha 109 spp., and Jatropha 50 spp.), whereas 24 genera contain fewer than 10 species. Enriquebeltrania is the only endemic genus, but 413 (57 %) species are endemic. The family is distributed from sea level to 3,600 m and is found in nearly all types of vegetation. The states with the greatest diversity are Oaxaca (247 spp.), Jalisco (210 spp.), Chiapas (196) and Veracruz (189 spp.). Conclusions: Our taxonomic and floristic understanding of the family is incomplete, and few genera have a modern revision or monograph. Twelve species are included in the NOM-059-(SEMARNAT 2010), and an additional 77 are at risk following the criteria of the IUCN Red List. It is imperative to conduct more research on taxonomy, distribution, and conservation.

As part of the systematic study of the tribes Ditaxeae and Adelieae (Acalyphoideae-Euphorbiaceae), here we compile and present a taxonomic synopsis for the South American taxa of Argythamnia, Chiropetalum, and Philyra. We recognize 22 species for Argythamnia, including one herein described as a new species, 20 species and one variety for Chiropetalum, and a single species for Philyra. We also designate 22 lectotypes, a new synonymization and a status novum, in addition to keys for each genus, distribution maps for all taxa, analysis of collection density in South America for each genus, and taxonomic and ecological comments for all taxa.

The state of Michoacán, Mexico is moderately diverse in Crassulaceae, with 38 species documented to occur there. In this article, two new species of Crassulaceae endemic to the Sierra Madre del Sur of Michoacán are described and illustrated with photos; a new state record is also reported. Echeveria coalcomanensis is known from a single rock outcrop in humid pine-oak forest at 2000 m in the Sierra de Coalcomán. It is placed in series Valvatae based on the inflorescence of cincinni, imbricate bracts, and valvate petals. The species can be easily distinguished from other members of the series by having green, ovate to deltoid leaf blades with a reddish acuminate apex. Sedum larai occurs at two localities separated by 90 km. One is found at the ecotone of oak forest and tropical deciduous forest at 1200 m, the other in pine-oak forest at 2138 m. The new species is similar to two species of Sedum sect. Fruticisedum, S. bourgaei and S. guadalajaranum, from which it differs by being a dwarf, rhizomatous herb with delicate, unbranched stems to 11 cm long. Sedum salazarii was previously known only from western Guerrero and is here reported 200 km to the west in the Michoacán, where it occurs in pine-oak forest and cloud forest at 2300 to 2500 m.